This invention relates to the field of communications devices and, more particularly, to devices including a channel scanning feature.
There are many systems in the field of communications which use channel scanning. The simplest system would begin at channel #1 and, if it is busy, proceed to the adjacent channel, then the next, etc., or perhaps start at the last channel used by the device and move to the next one. In some instances, however, there are valid reasons for not using this simple approach. If, for example, it is necessary to spread channel usage as evenly as possible over all of the available channels, it would be better to make the allocation of the initial channel in some random fashion. This is not difficult to accomplish, but channel interference problems would still remain since it is usually necessary to prevent multiple units from using the same channel at the same time. With a limited number of channels available within any given system, it is inevitable that occasionally two units will begin using the same channel at the same time. This is not a fatal flaw since each unit transmits for only a very brief period before listening on that same channel, and any unit hearing another transmission will automatically change channels. However, if both units are operating under a scanning system wherein the channel changed to is the adjacent channel, nothing will have been solved. The two units would still be competing for the use of that channel.
It is desired to solve these problems in a system wherein one unit, such as a cordless telephone, is paired with another unit, such as a base telephone unit, and an identification code is used to establish privacy for communications between the two.